foods Article Study on the Sleep-Improvement Effects of Hemerocallis citrina Baroni in Drosophila melanogaster and Targeted Screening to Identify Its Active Components and Mechanism Yuxuan Liang, Riming Huang, Yongchun Chen, Jing Zhong, Jie Deng, Ziyi Wang, Zhuojun Wu, Meiying Li, Hong Wang and Yuanming Sun * College of Food Science, South China Agricultural University, Guangzhou 510642, China; [email protected] (Y.L.); [email protected] (R.H.); [email protected] (Y.C.); [email protected] (J.Z.); [email protected] (J.D.); [email protected] (Z.W.); [email protected] (Z.W.); [email protected] (M.L.); [email protected] (H.W.) * Correspondence: [email protected] Abstract: Hemerocallis citrina Baroni (HC) is an edible plant in Asia, and it has been traditionally used for sleep-improvement. However, the bioactive components and mechanism of HC in sleep- improvement are still unclear. In this study, the sleep-improvement effect of HC hydroalcoholic extract was investigated based on a caffeine-induced insomnia model in Drosophila melanogaster (D. melanogaster), and the ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-ESI-Orbitrap-MS) and network pharmacology strategy were further combined to screen systematically the active con- Citation: Liang, Y.; Huang, R.; Chen, stituents and mechanism of HC in sleep-improvement. The results suggested HC effectively regu- Y.; Zhong, J.; Deng, J.; Wang, Z.; Wu, lated the number of nighttime activities and total sleep time of D. melanogaster in a dose-dependent Z.; Li, M.; Wang, H.; Sun, Y. Study on manner and positively regulated the sleep bouts and sleep duration of D. melanogaster. The target the Sleep-Improvement Effects of screening suggested that quercetin, luteolin, kaempferol, caffeic acid, and nicotinic acid were the Hemerocallis citrina Baroni in main bioactive components of HC in sleep-improvements. Moreover, the core targets (Akt1, Cat, Drosophila melanogaster and Targeted Ple, and Sod) affected by HC were verified by the expression of the mRNA of D. melanogaster. In Screening to Identify Its Active summary, this study showed that HC could effectively regulate the sleep of D. melanogaster and Components and Mechanism. Foods further clarifies the multi-component and multi-target features of HC in sleep-improvement, which 2021, 10, 883. https://doi.org/ 10.3390/foods10040883 provides a new insight for the research and utilization of HC. Academic Editor: Massimo Castellari Keywords: Hemerocallis citrina Baroni; liquid chromatography coupled with mass spectrometry sleep; Drosophila melanogaster; network pharmacology; mRNA expression Received: 12 March 2021 Accepted: 15 April 2021 Published: 17 April 2021 1. Introduction Publisher’s Note: MDPI stays neutral Sleep is a complex physiological process influenced by many factors [1]. The sleep with regard to jurisdictional claims in disorders of the population keep increasing in modern society because of the changes in published maps and institutional affil- lifestyle and environment [2]. Emerging evidence indicates that inadequate sleep can have iations. many negative effects on health, such as obesity, heart disease, anxiety, and depression [3–7]. Epidemiological studies have shown that the prevalence of sleep disorders ranges from 3.9% to 22.0% in the world population [8–11]. Drug therapy is still the main method of sleep- improvement; however, more and more studies have paid attention to dietary supplements Copyright: © 2021 by the authors. in avoiding dependence, addiction, and other side-effects induced by drugs [2,12–15]. Licensee MDPI, Basel, Switzerland. Similar to mammalian sleep, circadian rhythms of D. melanogaster have been quantified This article is an open access article as a sleep/wake activity and neuromodulation of sleep behavior [16], and the locomotor distributed under the terms and activity of D. melanogaster is often used to measure sleep/wake activity [17]. At present, conditions of the Creative Commons the spontaneous locomotor activity of D. melanogaster is quantified using a PC-based Attribution (CC BY) license (https:// locomotor activity monitoring system, which records the locomotor activity of individual creativecommons.org/licenses/by/ D. melanogaster based on the interruption of an infrared beam. It is able to monitor the 4.0/). Foods 2021, 10, 883. https://doi.org/10.3390/foods10040883 https://www.mdpi.com/journal/foods Foods 2021, 10, 883 2 of 15 locomotor behavior of D. melanogaster over a longer period of time under standardized living conditions, as well as to measure the sleep parameters of D. melanogaster [18]. The previous studies have defined the duration of sleep, the number of sleep cycles, and the average duration of each sleep in Drosophila [13,19,20]. Therefore, models of D. melanogaster have been valuable in the discovery of novel sleep regulators [17]. Hemerocallis citrina Baroni (HC), as an edible plant, is widely grown in Asia with high economic value due to its good taste and health-promoting properties, and it has a long history of being used to ameliorate sleep-related disorders [21–23]. However, the unclear material basis and molecular mechanisms of HC in sleep-improvement re- strict its further development and application. Phytochemical analysis revealed that HC contains many bioactive components such as flavonols, anthraquinones, and polyphe- nols [24]. Furthermore, previous studies have shown that HC possesses anti-depression and anti-inflammatory effects [23,25–27]. Among them, Du et al. reported that the main compounds responsible for its antidepressant activity are flavonoids (especially rutin and hesperidin) [22,28]. Furthermore, a few studies have indicated that some single com- pounds such as rutin, hyperoside, and caffeic acid might possess the potential function of improving sleep [29–33], though these studies mainly focused on the bioactivity of a single compound. However, food provides a characteristic combination of multiple nutrients in one group that work together to play an essential role. Therefore, we speculate that there are multiple compounds in HC that play a role in sleep-improvement. With the development of pharmacology, bioinformatics, and network science, Hopkins proposed the concept of “network pharmacology” in 2008 [34], which provides novel insights to reveal the coordinated interaction among multi-components, multi-targets, and multi-pathways, and to deepen the understanding of complex diseases at the system level [35,36]. So, in this study, the sleep-improvement effect of HC was firstly investigated based on the caffeine-induced insomnia model in D. melanogaster. Then, high-resolution UHPLC-ESI-Orbitrap-MS was used to analyze the composition of HC. On this basis, the network pharmacology strategy was used to screen bioactive compounds and identify the mechanism of HC in sleep-improvement. Moreover, the transcription levels of core targets of the network were further verified. 2. Materials and Methods 2.1. Materials Commercial Hemerocallis citrina Baroni (flower buds) was obtained from Qidong county, Hunan province. Acetonitrile hypergrade for liquid chromatography coupled with mass spectrometry (LC-MS) LiChrosolv® was bought from Merck KgaA (Darmstadt, Germany), and methanol hypergrade was purchased from SIMARK (Tianjin, China). Ultra- pure water was prepared using the Unique-R10 system from Research Water Purification Technology Co. Ltd. (Xiamen, China). 2.2. Preparation of HC Extract Two hundred grams of HC was ground to powder and extracted three times in 2000 mL of 60% ethanol under a temperature of 25 ◦C, each time for 24 h. The combined ethanolic extract was centrifuged at 12,000 rpm for 15 min, and then the supernatant was concentrated under reduced pressure on a rotary evaporator (45 ◦C, 60 hpa). Part of the concentrate was lyophilized for 72 h to obtain lyophilized powder and stored at −20 ◦C. Additionally, part of the concentrate was filtered by a 0.22 µm filter membrane and then stored at −4 ◦C until UPLC-orbitrap-MS analysis. 2.3. Drosophila Stocks Wild-type D. melanogaster (Canton-S strain) were purchased from the Core Facility of Drosophila Resources and Technology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences. The flies were raised in standard medium (5% sucrose, 8% Foods 2021, 10, 883 3 of 15 cornmeal, 4% dried yeast, 1% agar, and 0.5% propionic acid) at 25 ◦C in 12:12 h light: dark cycles. Male flies (3-day-old) were collected under CO2 anesthesia for formal experiment. 2.4. Measurement of Locomotor Activity The food used in the measurement of locomotor activity was made up of 1% agar and 5% sucrose. Agar-sucrose food containing 0.1% caffeine was made. On this basis, 0.625%, 1.250%, and 2.500% of HC extract were add to the agar-sucrose food containing 0.1% caffeine, respectively. Each group contained 19 fruit flies. D. melanogaster were individually transferred in separate plastic tubes and were monitored through the Drosophila Activity Monitoring System (DAM; TriKinetics, Waltham, MA, USA). Monitoring was performed for 3 days under conditions of constant darkness at 25 ◦C and 60% relative humidity, and locomotor activity was taken every minute. The sleep of D. melanogaster was defined as no locomotor activity observed within 5 min [37], and the number of sleep bouts and sleep duration was counted by excel [13,38]. 2.5. UHPLC-Orbitrap-MS Analysis A Q Exactive-Orbitrap Mass Spectrometer (Thermo Fisher Scientific, Bremen, Ger- many), equipped with an electrospray ionization (ESI) source working in a positive model and a negative model was used for accurate mass measurements. Liquid Chromatog- raphy analysis was performed using a Dionex UltiMate 3000 (Thermo Fisher Scientific, Bremen, Germany) equipped with a quaternary pump and a thermostated autosampler. Chromatographic separation was accomplished with an Agilent InfinityLab Poroshell 120, 4.6 mm × 150 mm, 2.7 µm column were used (Agilent Infinity Lab, Wilmington, DE, USA). The detailed operation was performed according to the previous method with slight modifications, and it is presented in the Supplementary Material [39].